Fisica
A 5.0-kg object slides down a surface inclined at an angle of 30o from the horizontal. Friction may be neglected. The total distance moved by the object along the plane is 10 meters. The work done on the object by the normal force exerted on the object by the surface is most nearly
·0 kJ
An object moves halfway around a circle of radius R. An inward radial force of magnitude F is The work done on the object by the radial force being exerted on it is
·zero
A person exerts a constant force of 45 N directed at angle 100 N to pull it from one end of a room to another, a distance of 4.0 m. Given that the vertical component of the force is 12 N, calculate the work done by the person on the crate.
·1.7 x 10^2 J
A donkey is attached by a rope to a wooden cart. The rope makes an angle of 23o to the horizontal. The tension in the rope is 210 N. If the cart is pulled horizontally along the ground with a constant speed of 6.0 km/h, calculate how much work the donkey does on the cart in 35 minutes.
·680 kJ
A variable force is represented on an F-versus-x graph. Which of the following is the work done by this force?
·the area bounded by the curve and the x axis
An object on which a variable force is exerted travels a distance of 20 m in a straight line in the same direction as the force. The graph shows the force exerted on the object as a function of the position. What was the total work done by this force on the object during the full 20-m trip?
·60 J
A block is pushed on a horizontal surface by force, . The surface exerts a force of friction on the block. If the block undergoes a displacement d at constant velocity, the net work done on the block
·is zero.
A 6.0-kg block slides from rest at position A down a frictionless incline to position B. the block at B is
·4.4 m/s
A skier of mass 50 kg is moving at speed 10 m/s at point P1 down a ski slope with negligible friction. What is the skier’s kinetic energy when she is at point P2, 20 m below P1?
·12300 J
A mass m = 2.5 kg is sliding along a frictionless table with initial speed v as shown in the figure. It strikes an uncoiled spring of force constant k = 500 N/m and compresses a distance of 5.0 cm. The initial speed v of the block was
·0.71 m/s
A mass on a frictionless surface is attached to a horizontal spring of spring constant k and set into motion by being displaced from its equilibrium position xi a distance A and released. Which of the following graphs best represents the kinetic energy as a function of displacement when the mass moves on its own from position xi to position A? ( d ) iII
A ball of mass m is dropped from an initial position at height h1 above a reference point. The ball is observed in three positions A, B and C, as indicated in the figure. Which of the graphs shown best represents graphs of the kinetic energy K, gravitational potential energy U, and total mechanical energy E of the ball-Earth system at positions A, B and C?
·A →Graph (F), B →Graph (E), C →Graph (A)
An object falls through the atmosphere gaining 20 J of kinetic energy. If air resistance is not negligible, how much gravitational potential energy is transferred out of the object-Earth system?
·more than 20 J
A woman on a bicycle traveling at 10 m/s on a horizontal road stops pedaling as she starts up a hill inclined at 3.0o to the horizontal. If friction forces are ignored, how far up the hill does she travel before stopping?
·97m
A simple pendulum has a bob of mass m. fixed at I. At position A, the string is horizontal and the bob is at rest. The bob is released from I and swings to B, where the string is vertical. The tension in the string when the bob first reaches I is
·3Mg
A roller coaster starts from rest at point A. If you ignore friction and take the zero of potential energy to be at C,
·the kinetic energy of the coaster at C will be equal to its potential energy at A
A force of 6.00 N directed at the angle of 40.0o relative to the ground moves a 1.00 kg block a distance of 0.250 m in 2.00 s. What is the power delivered to the block by the force?
·0.574 W
A uniform 12-inch ruler has a 5-g mass at the “1-inch” mark, and a 10-g mass at the “7-inch” mark. Where is the system’s center of mass?
·Between the “1-inch” mark and the “6-inch” mark
A wheel is rotating at 30 rev/min. The angular velocity of the wheel is
·i rad/s
A wheel on a car is rolling without slipping along level ground. The speed of the car is 36 m/s. The wheel has an outer diameter of 50 cm. The speed of the top of the wheel is
·72 m/s
A wheel rotates with a constant nonzero angular acceleration. remains constant in magnitude?
·tangential acceleration
A perfectly spherical orbiting communications satellite is in a circular orbit about Earth. The torque exerted on the satellite by the gravitational pull of Earth is
·zero.
An object that moves with a constant speed in a circle
·has no work done on it
A cylinder (Icylinder = cylinder is _____. MR2) rolls along a level floor with a speed
·¾ mv^2
If mechanical work is done on an object, the object must
·accelerate
If the momentum of an object of mass M is doubled, its kinetic energy will be multiplied by a factor of
·4
In a center-of-mass reference frame for a system with no external forces applied to it
·the total momentum is zero
Negative work means
·the angle between the displacement vector and force vector is larger than 90º
The SI unit of energy can be expressed as
·kgm2s2
Two skiers start at the same place and finish at the same place. poles during the trip. They both just slide along their chosen path. Skier A takes a straight, smooth route to the finish whereas Skier B takes a curvy, bumpy route to the finish. If you assume that friction is negligible, which of the following statements is true?
·Skier A has the same speed as skier B at the finish.
The graph represents the force F exerted on a object plotted versus the displacement x of the body in The total work done by the force from x = 0 to x = x is
·1/2 mx2 +bx
The block shown is released from rest on a frictionless ramp. Its speed when it reaches the level portion of the surface on which it is sliding will be
·7.67 m/s
The block shown is released from rest on a frictionless ramp. It slides 9.0 m on the rough, level surface before stopping. What is the coefficient of kinetic friction between the block and the level surface?
·0.33 m/s
The surface shown in the figure is frictionless. The block is released from rest. What will be the maximum compression of the spring? (Provide three significant digits in the final answer.)
·0.989 m
Two identical air-hockey pucks are moving on an air-hockey table with an x–y axis drawn upon it. Puck A has a velocity of 5 m/s at an angle of 35 degrees above the x-axis. Puck B has a velocity of 6 m/s at an angle of 70 degrees above the x-axis. Which puck has a larger momentum in the x-direction?
·Puck A
Two objects, one of mass M, and the other of 5M rest on a horizontal frictionless table with a compressed spring of negligible mass between them. The spring is released and each object gains kinetic energy. The object of mass M gains
·5/6 of the energy
Two students, initially at rest, sit on carts with frictionless wheels. The mass of student 1 and her cart is M, and the mass of student 2 and her cart is 1.5M. The students push against each other and roll in opposite directions. If student 2 moves with velocity , what is the velocity of student 2?
·+ 2/3 – v
The condition necessary for the conservation of linear momentum in a system is that
·the net external force on the system is zero.
Two objects of equal mass travel in opposite directions with equal speeds. If they collide in a perfectly elastic collision, then, just after the collision, their velocities will be
·equal in magnitude but opposite in direction to their original velocities
The center of mass of a system of particles is so defined that
·its location depends only on the masses of the particles and their locations.
Two identical objects, A and B, are placed on a horizontal platform that is rotating about an axis through its center at a constant angular velocity. A is located at a distance R from the axis of rotation, and B is located at a distance 2R. The angular velocity of A to the angular velocity of B.
·is equal to
The London Eye, a giant Ferris wheel, has a diameter of 135 m. It revolves at a constant rate and takes 30 minutes to complete one revolution. What is the linear velocity of a rider in a capsule that is located at the perimeter of the wheel?
·0.24 m/s
The rotational inertia of an object about an axis depends on the
·mass distribution about the axis.
The diagrams show the application of a force to a level arm. Which diagram has the largest (magnitude) torque about the hinge?
·They are the same
Which of the following statements about energy is true:
·An object’s or system’s energy is related to its ability to do work.
What is the net work done on a 1500-kg car when it slows from an initial speed of 96 km/h down to 56 km/h in a distance of 55 m?
·–3.5105J
Which of the following statements is NOT correct?
·The force of friction is a conservative force.
What is the escape speed from the Sun, beginning (from rest relative to the Sun) at the orbit of Earth, R = 1.50 108 km? (Given: G = 6.67 10–11 N m2/kg2; mass of the Sun = 2.0 1030 kg.)
·4.2 x 10^4 m/s
What physical quantity is represented by the slope of the curve shown on the graph?
·angular acceleration
You are pedaling a bicycle at 9.8 m/s. The radius of the wheels of the bicycle is 51.9 cm. The angular velocity of rotation of the wheels is most nearly
19 rad/s